Bwindi has more gorilla families, more trekking sectors and the higher success rate — but thicker forest and steeper ground. Nkuringo and Rushaga in the south are the toughest and quietest; Buhoma in the north is the most developed and the easiest to reach.
Mgahinga is a single habituated family, more open walking, often a shorter day, and far fewer people. The catch: the family occasionally crosses the border into Rwanda, and treks are suspended until it comes back.
If it’s your only gorilla trek and you want the surest thing, pick a Bwindi sector matched to your fitness. If you’re also doing golden monkeys or climbing a volcano, Mgahinga earns its place.